The present invention is concerned with improved MEMS devices and techniques as for use in optical switching and related applications; being more particularly, though not exclusively, directed to improvements in such devices wherein the MEMS device is flip-chip bonded to an optically transmissive printed-circuit substrate, as of the type, for example, described in co-pending application Serial No. 09/829,318 of co-applicant Vernon Shrauger entitled Improved Critically Aligned Optical MEMS Dies For Large Packaged Substrate Arrays and Method Of Manufacture and filed Apr. 9, 2001, and of common assignee, Axiowave, Inc. Such integrated optical substrates enable integration with passive and active optical devices therein or therealong, such as lenses, optical wave guides, lasers, photodetectors and the like, for optical interaction with the MEMS device containing electrical signal-controllable tiltable or orientable light-reflecting and directing mirrors, or other light-directing devices, such as valves, moving arms, shutter or other electromechanical structures and the like.
As explained in said copending application, light-transmissive substrates had been previously used for such purposes as serving as a package lid or the like; and now, in accordance with the invention of said co-pending application, with said passive and active optical devices integratable in or along the substrate for enabling controlled alignment or fixed optical light paths to and from the tiltable MEMS mirrors or the like, for switching the light signals amongst communication optical fiber bundles. The use of flip-chip bonding of superposed printed circuit optically transmissive substrates (circuits for optical addressing, etc.) by interposed spacer layer posts, enables non-interfacing unrestricted mirror tilting of the MEMS devices within the mirror wells, and the attachment with tight alignment of pluralities of MEMS devices in large packaged arrays. Such novel arrays of optically and electrically interacting optical MEMS dies are physically and electrically integrally attached upon an optically transmissive (preferably transparent) printed circuit substrate that is monolithically formed with one more optical components, such as lenses, for providing fixed optical path alignment and interaction therebetween, and with provision for the integration also of active optical components such as lasers and photodiodes and the like.
The electrical signal-controlled mirror deflecting, tilting or orienting about a torsion spring, hinge or other micro-actuator of prior MEMS devices, is generally effected with the aid of electrodes disposed in the bottom of the mirror wells and to which electrical voltages are applied responsive to, for example, desired optical path-switching signal controls. Such microtorsion actuators are described, for example, in an article entitled xe2x80x9cPull-In Study of an Electrostatic Torsion Microactuatorxe2x80x9d by Degani et al. appearing in the Journal of Microelectromechanical Systems, Volume 7, No. Dec. 4, 1998. The prior use of such substrates with tiltable mirror light path modulation control is illustrated, for example, in U.S. Pat. No. 6,046,840, having, however, inherent limited deflection angle of the tiltable mirror. And other proposals involving signal-deformable multi-layer mirrors are illustrated by exemplary U.S. Pat. Nos. 5,835,255 and 5,949,801.
The present invention, however, through the use of the flip-chip bonded optically transmissive printed control circuit substrates of said co-pending application, has now further enabled greater and more facile positioning control of the electrical signal actuation of the MEMS mirrors; and, indeed, the generation of greater forces, including complementary forces, for such actuation than have heretofore been achievable with the bottom well field-generating electrodes of the prior MEMS devices. With electrodes both above and below the moving MEMS structure higher operating bandwidth and more stable control is possible. Electrostatic restoring forces may also be utilized instead of the mechanical restoring forces of elastic springs. This is achieved through the use of upper transparent electrodes in the optically transmissive substrate that do not impair the optical transmission therethrough and that enable supplementing the lower mirror-actuating field generated in the mirror well by the customary bottom electrodes therein, with an additional upper electrical control field from the topxe2x80x94this also enabling the above-mentioned desirable complementary type of control, as well.
A principal object of the invention, thus, is to provide such a new and improved MEMS device, particularly and preferably of the flip-chip bonded optically transmissive substrate structure, that enables the ready use of supplemental electrical control fields for orienting the MEMS mirrors or similar elements and that removes limitations in the operation of current MEMS devices.
A further object is to provide transparent electrodes with such optically transmissive structures, and a novel method for attaining such improved results.
Other and further objects will be explained hereinafter, and are more particularly delineated in the appended claims.
In summary, however, from one of its important aspects, the invention embraces an optical-electrical MEMS device carrying an electrical signal-controllable orientable mirror and covered by an optically transmissive substrate mounted spaced above the mirror; and means for generating an upper electrical field in the space above the mirror and under said substrate for controlling the mirror orientation, preferably through the use of transparent electrodes carried by said substrate.
Preferred and best mode designs and embodiments are later more fully explained.